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During the total solar eclipse on April 8, the Sun will momentarily transform into a gravitational lens, changing the shape of some stars. This effect was observed for the first time in 1919 in Brazil and Africa, proving Albert Einstein’s theory.
In 1911, Einstein revived Isaac Newton’s proposal, stating that light would be affected by gravity. This idea, until then discarded by scientists who came after Newton, now made more sense thanks to the new Einsteinian theory of gravitation.
The General Theory of Relativity demonstrated that gravity is, in fact, a distortion of space-time caused by the mass of objects. This completely changed the perception of the universe and explained confusing things like the orbit of Mercury.
However, such a revolutionary theory would require observational proof, which occurred numerous times in the following decades. One of the first of these occurred in 1919, during a total eclipse observed in Brazil, in the city of Sobral, Ceará.
The experiment is simple: first, you have to wait for the eclipse to darken the sky, practically turning day into night, allowing some stars to become visible. If Einstein was right, some of them would be “deformed”.
The mass of the Sun is about 330,000 times greater than that of the Earth, enough to create a strong gravitational field around it. In general relativity, this means a considerable distortion in spacetime.
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Although light travels in a straight line, it must obey the topography of space-time — similar to a car obeying the curves of a road. For an observer on Earth, the result is a magnified image of the star, hence the name gravitational lensing.
During the April 8 eclipse, some stars well aligned with the Sun and Earth — but not close enough to be hidden by the solar disk — will be visible and will look subtly different from those seen at night.
Observers will generally not notice the effects of gravitational lensing on these stars, and even astronomers must measure in advance the positions and brightness of stars during the nights before the eclipse.
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Even without the instruments to make measurements, it is exciting to observe eclipses, an incredible phenomenon in itself, knowing that they helped to establish Einstein as the greatest genius in contemporary science.
Source: The Conversation
